Program centralled, cam operated switch assembly

ABSTRACT

A heavy duty contactor mechanism for refrigeration compressor motors is directly actuated by a timing mechanism controlled by a thermostat. The timing mechanism protects against false starts from thermostat vibration, and interposes a delay between stopping and starting of the compressor sufficient to allow pressures to equalize. Power for operating the contactor switches is stored in a spring while the timer motor is running through the delay period.

United States Patent Harris Dec. 30, 1975 [5 PROGRAM CENTRALLED, CAM 3,370,474 2/1968 Harper 200 153 T x 3,599,006 8/1971 Harris 200 39 R x OPERATED SWITCH ASSEMBLY John L. Harris, Clearwater, Fla.

Assignee: Deltrol Corporation, Bellwood, 111.

Filed: Mar. 18, 1974 Appl. No.: 451,886

Related U.S. Application Data Division of Ser. No, 321,715, Jan. 8, 1973, Pat. No. 3,833,818, which is a division of Ser. No. 179,422, Sept. 10, 1971, Pat. No. 3,745,293.

Inventor:

U.S. C1. 200/38 R; 200/38 B; 200/153 LB;

335/73 Int. Cl. l-10lh 43/00 Field of Search 200/33-39, 200/153 T, 153 LB, 40, 41; 335/21, 28, 6377 References Cited UNITED STATES PATENTS 11/1966 Anson 200/153 LB Primary ExaminerJames R. Scott [57] ABSTRACT A heavy duty contactor mechanism for refrigeration compressor motors is directly actuated by a timing mechanism controlled by a thermostat. The timing mechanism protects against false starts from thermostat vibration, and interposes a delay between stopping and starting of the compressor sufficient to allow pressures to equalize. Power for operating the contactor switches is stored in a spring while the timer motor is running through the delay period.

3--'Claims, 24 Drawing Figures 3 STANDBY U.S. Patent Dec. 30, 1975 Sheet1of3 3,930,132

3 STAN D BY I60 I65 I62 l4 U.S. Patent Dec. 30, 1975 Sheet 2 of3 3,930,132

INITIAL DELAY PERIOD START AND SHORT CYCLE ADDER PERWD 8 OFF EQUAUZATION DELAY PEPJOD EQUAUZATION DELAY PERIOD US. Patent Dec. 30, 1975 Sheet 3 of3 PROGRAM CENTRALLED, CAM OPERATED SWITCH ASSEMBLY CROSS REFERENCE TO RELATED APPLICATION This application is a division of my application Ser. No. 321,715 filed .Ian. 8, 1973, now US. Pat. No. 3,833,818 which is in turn a division of my application Ser. No. 179,422 filed Sept. 10, 1971, now US. Pat. No. 3,745,293.

BACKGROUND OF THE INVENTION In air conditioning and refrigeration systems having motors of three H.P. and above, it is necessary to use a magnetic starter or contactor for handling the current to the compressor motor. These devices include a large expensive electro-magnet, the coil currentof which is controlled directly by a thermostat or by a relay controlled by the thermostat.

Unless a time delay mechanism is interposed between the thermostat and coil, damage can result from false starts caused by vibration of the thermostat causing the contactor to bounce in and out. This causes rapid making and breaking of the heavy starting inrush current to the motor which can damage both the starter contacts and the motor. Also if the compressor is stopped and immediately restarted, the suction and head pressures on the compressor have a wide differential and the motor will usually not have sufficient starting torque to start the compressor under these conditions. A delay in restart sufficient to allow the pressures to equalize is needed. In some cases, malfunctioning of a part of the system causes the safety controls to stop the compressor. This condition causes rapid starting and stopping (short cycling) of the compressor which is damaging to both the compressor and its motor.

These considerations have led to use of timing systems between the thermostat and compressor contactor which provide the necessary safequarding delays. These systems are relatively complex and expensive.

.BRIEF SUMMARY OF INVENTION In applicant's invention, the usual magnetic starter is replaced by a new type of starter directly operated by the timing mechanism which provides the desirable time delay features. This eliminates the noise of magneticstartcrs slamming in and out and also eliminates the loud humming usually occuring with magnetic starters. In addition, it substantially simplifies the control system which reduces costs. It also reduces installation costs as an entire control system is included in a single component. I

In applicants invention, the contactor mechanism is similar in appearance to the usual magnetic starter and the movable contacts are carried by a slide in the same general manner. This slide is actuated by a cam follower which is spring biased against a main cam driven by a timer motor. The control also includes an electromagnet controlled by a thermostat.

On call for cooling, the electro-magnet is energized which closes a switch for the timer motor. After a fifteen second delay, the cam follower rides down a dropoff on the main cam. During this downstroke the cam follower is engaged to the switch slide bya closing pawl and pulls the slide down to engage the contacts, starting the compressor. At the end of the downstroke of the slide. the closing pawl is releasedand the slide is now held down by a holding pawl.

During the downstroke of the cam follower, it advanced the main cam which in turn advanced a timer motor switch cam which maintains the timer motor switch closed independently of the electro-magnet. The timer motor now runs for approximately two minutes at which time the motor switch opens even though the electro-magnet is still energized.

When the thermostat is satisfied, it drops out the electro-magnet which releases the holding pawl. This allows the switch slide to return to its upper position under its own bias, opening the contacts to stop the compressor. This movement of the switch slide recloses the timer motor switch. The timer now runs for approximately five minutes back to the starting position where the timer motor switch opens. During this time, the cam follower is driven back to its upper position and power is stored in its biasing spring for the next cycle.

It is important that the contactor switches open without requiring operation of the timer motor. This is necessary for safety and also to insure proper recycling after a power interruption.

The primary object of the invention is to provide a timing mechanism-for actuating a load switch operator to close the switches under the control of a condition responsive device or master controller, which releases the operator instantly for opening the switches, and which utilizes power provided by the timer motor to actuate the operator with rapid action.

When the releasing of the switch operator is achieved by an electro-magnet releasing a latch, it is desirable to use as small an electro-magnet as possible. It is a further object of the invention to reduce the force required for releasing the latch by providing a motion transmitting means between the switch operator and latch giving a mechanical advantage to the latch in holding the switch operator. 7

Another object of the invention is to provide an arrangement in which the holding latch has a plurality of latching surfaces allowing for immediate latching engagement in spite of the increased travel resulting from the mechanical advantage.

A further object of the invention is to provide an arrangement for dampening the movement of the switch operator to obtain controlled speed of contact make and break.

Other objects will appear from the following detailed description and appended claims.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a side-view partly in section of'a time delay contactor embodying the invention, this section being taken on line 1-1 of FIG. 2. g

' FIG.2 is an internal front view taken on line 22 of FIG. I.

FIG. 3 is a top view of the contactor.

FIG. 4 is another internal front view taken online 4-4 of FIG. 1.

FIG. 5 is a side view partly in section of FIG. 4.

FIG. 6 is a bottom view taken on lines 66 of FIG. 4.

FIGS. 7, 8, 9 and I0 are views similar to FIG. 4 but showing the different combinations of positions assumed by the parts during a typical cycle of operation.

FIG. I1 is a schematic wiring diagram showing the application of the invention to an air conditioning system.

FIG. 12 is a view similar to FIG. 2 but showing the positions of the switch operating mechanism when the switches are closed.

FIG. 13 is a modified schematic wiring diagram.

FIG. 14 is a partial view similar to FIG. 12 butshowing the positions of the parts when the contactor first opens. FIG. 15 is a plan view of the cam follower.

FIG. 16 is a side view of FIG. l5.

FIG. 17 is a front view of the switch operator slide.

FIG. 18 is a sectional view taken on line 18-18 of FIG. 17.

FIG. 19 is a detailed view of the tooth form on the ratchet wheel.

FIG. 20 is a top view of FIG. 21.

FIG. 21 is a rear view taken on line 21-21 of FIG. 1 with the rear plate removed. I

' FIG. 22 is a sectional view taken on line 2222 of FIG. 21. I

'FIG. 23 is an enlarged sectional view showing the cam follower roller arrangement.

FIG. 24 is an enlarged sectional view of the camshaft assembly.

DETAILED DESCRIPTION OF INVENTION Referring to FIGS. 1 and 2, reference character 1 indicates a base plate upon which the mechanism is mounted. This base plate carries a U-shaped internal bracket 2 thelower leg 3 of which is attached to the base plate '1. The bracket 2 also includes an upwardly extending portion 4 which supports the operating mechanism. This bracket also includes a horizontal portion 5 which serves as one support for the switch block generally indicated as 6. Also mounted on the base plate 1 is an end bracket generally indicated as 7. This end bracket includes a horizontal portion 8 attached to the base plate, an upwardly extending portion 9, and a horizontal portion 10 which serves as the other support for the switch block 6. As shown in FIG. 6, the bracket 7 also includes side members 11 and 12 which serve to form an enclosure for the operating mechanism. Also as shown in FIG. 6, the upwardly extending portion 4 of bracket 2 includes rearwardly extending cars 13 and 14 which are attachable by screws (not shown) to the side members 11 and 12 respectively.

The switch block 6 illustrated is for a three pole switch and is formed with three channels 16, 17 and 18 (FIG. 2) which receive three identical switches generally indicated as 19. As shown in FIG. 1, each switch 19 includes a left hand terminal bracket 20 and a right hand terminal bracket 21 which are held in place by terminal screws 22 which are threaded into suitable inserts 23'molded into the switch block 6. In order to save space, the switch block 6 is reduced in thickness at the center portion and the terminal brackets 20 and 21 are offset so as to lower the locations of the stationary contacts 25 and 26 carried by these brackets.

Each switch also includes a movable contact bar 27 carrying movable contacts 270. The three movable contact bars 27 are carried and actuated by a slide 28 (FIG; 2). This slide extends transversely across the switch block 6 and has extensions 29, 30 and 31 which extend upwardly through openings in the switch block and support the movable contact bars 27. As shown in FIG. 1 the slide extension 30 is formed with a shoulder which supports the movable contact bar 27. The slide extension is also formed to receive a spring retainer 33 for an overtravel spring 34. The switch block 6 is secured in place by a pair of screws 36 which extend into the horizontal portion 5 of bracket 2. The block 6 is 4 also secured by a pair of screws 37 which extend into the horizontal portion 10 of the case bracket 7.

As shown in FIGS. 2 and 5 the lower end of slide 28 is slideably mounted on a pair of studs 39 and 40 which are attached to the vertical case member 9. Each stud includes a main portion 41 and a reduced portion 42 providing a shoulder 43. As shown in FIG. 2 the slide 28 is formed with slots 44 and 45 which fit over the reduced portions 42 of the mounting studs. The shoulders 43 on the mounting studs serve to locate the slide 28 in spaced relationship with the rear case member 9. The slide is held in place on the reduced portions 42 by washers .46 suitably attached to the studs.

The construction of slide 28 is shown in detail in FIGS. 17 and 18. This slide is preferrably molded and includes a transverse upper member 48 which supports the switch bar extensions 29, 30 and 31. The slide 28 also includes side members 49 and 50 which extend downwardly and which are molded L-shaped at the lower ends shown in FIG. 17. Extending between the lower ends of side members 49 and 50 is a cross over member generally indicated as 51. This cross over member is formed of thin webs 52 and 53 joined at their lower edges by a forwardly extending section 54. The web 52 is formed with an offset providing a shoulder 55 the purpose of which will appear as this description proceeds.

Extending downwardly from the transverse section 48 is a gear rack section 56 provided with gear teeth 57 and formed with a channel 58 which also extends through the transverse prtion 48. Extending forwardly from the slide 28 is a projection 59 which supports the closing pawl 60 as shown in FIGS. 1 and 2. Also extending forwardly from the transverse section 48 is a cam member 69. This cam member 69 includes a horizontal section 70 which projects forwardly from the cross over section 48. The cam member also includes a downwardly extending extension 71 having camming surfaces 72 and 73. A slot 74 is formed in the transverse section 48 adjacent the cam extension 70 as shown in FIG. 18.

Mounted inside the confines of switch operator slide 28 is a cam follower generally indicated as 80. The construction of this cam follower is shown in detail in FIGS. 15 and 16. This cam follower has a main generally U-shaped portion consisting legs 81 and 82 connected by a horizontal leg 83. This cam follower also includes two upward extensions 84 and 85 which are offset rearwardly as shown in FIG. 16. Extending forwardly of the cam follower is a lug 86, and mounted on the rear of the cam follower is a roller 87. The cross over section 83 of the cam follower is formed with curved upper surfaces 88 and 89 which serve as camming'surfaces as will be described.

The cam follower 80 is mounted within the confines of slide 28, the legs 81 and 82 being in front of webs 52 and 53 of the slide 28. Extension 85 of the cam follower fits into the slot 58 in the slide and extension 84 of the follower fits into slot 74. As shown in FIGS. 2 and 5 the outer edges of the legs 81 and 82 of the cam follower fit in between the reduced portions 42 of the studs 39 and 40 and are held in place by washers 46. The cam follower is thus slideably mounted with the switch operator slide 28, being guided at its lower end by the studs 39 and 40 and being guided at its upper end by extensions 84 an 85 fitting into the slots 74 and 58 of the opera-tor slide.

As shown in FIGS. 2, 12 and 14 the closing pawl is pivotally mounted on stud 59 of the switch operator slide. This closing pawl includes a downwardly depending portion 89 formed to provide a latching surface 90 and a camming surface 91. The closing pawl is also formed with a releasing lever portion 92 and a disengaging lever section 93. The closing pawl 60 when in latching position as shown in FIG. 2 is engageable by the lug 86 formed on the cam follower.

The switch operator 28 is biased upwardly by coil springs 95 and 96 (FIGS. 5 and 21). The lower ends of these springs fit into extensions 97 molded on the back of the operator slide 28. The upper ends of these springs are supported on studs 98 attached to the case member section 9. The springs 95 and 96 thus serve to bias the switch operator means in a direction opening the switches.

As shown in FIGS. 1, 2 and 22 the cam follower roller 87 rides on a cam 100 which is loosely mounted on a shaft 101 which is staked into the enclosure plate 9. The cam 100 as shown best in FIG. 21 includes a high portion 102 and a low portion 103 connected by a drop off section 104. The cam also includes a gradual rise portion 105 which extends from the other side of the low portion 103 to the high portion 102. The cam 100 is driven in a clockwise direction as seen in FIG. 2, (counterclockwise in FIG. 22) by a gear 107 which is also supported on the shaft 101. This gear 107 is provided with a shoulder 108. As shown more clearly in enlarged FIG. 24 the gear 107 is provided with a slot 109 into which a stud 1 10 on cam 100 extends. This pin and slot arrangement provides a lost motion drive between the gear 107 and cam 100 and as shown in FIG. 21 the slot 109 is formed to provide in excess of 90 lost motion. This permits advancement of the cam relative to the gear the amount of lost motion provided by the lost motion drive means.

The gear 107 is driven by a timer motor 112 which is mounted on the enclosure plate 9 beneath the switch block 6. Preferrably the reduction gears are interposed between the timer motor output. In the embodiment of the invention illustrated the timer motor speed and gear reduction are selected to give one revolution of the cam 100 in approximately seven minutes.

The cam follower 80 is biased downwardly to cause the roller 87 to ride the cam by spring biasing means including springs 114 and 115 (FIG. 21). These springs are mounted on hubs 116 of identical spring levers 117.

' As shown in FIGS. 5 and 21, one spring lever 117 is mounted on the enlarged portion 41 of the stud 40 which also supports the switch operator 28 and the cam follower 80. The other spring lever 117 is mounted similarly on the stud 39. The spring levers 117 are provided with rearwardly extending studs 118 upon which the upper legs of springs 114 and 115 hear. The lower legs of these springs rest on horizontal section 8 of the rear housing member 7.

As shown in FIGS. 5 and 21 the spring levers 117 extend upwardly behind the cam follower 80 and are provided with rollers 119 which extend forwardly and ride the camming portions 88 and 89 of the cam follower 80. As shown in the enlarged FIG. 23, the roller 119 is formed with a slot 120 the inside surface of which rides the cam follower. As the spring levers 117 are accurately positioned by hubs 116, the grooves in rollers 119 serve to position the upper end of the cam follower which in turn positions the upper end of the switch operator 28 into which the cam follower fits.

This arrangement facilitates assembly of the unit as the switch operator is held in the correct position before installation of the switch block 6.

It will be apparent that the springs 114 and 115 serve to bias the spring levers inwardly and that the rollers riding the camming surfaces 88 will cam the switch operator downwardly when this motion is allowed by the cam 100. Preferably the camming surfaces 88 are characterized to reduce the rate of travel of the cam follower as it moves downwardly. This compensates for loss in spring tension of the springs 114 and 115 as the spring levers move inwardly and the cam follower moves downwardly. This arrangement also gives a relatively large motion per increment of movement of the spring levers when the switch operator is being moved to close the air gap between the stationary and movable contacts. It also gives relatively small motion of the cam follower per increment of movement of the spring levers after the contacts engage and provides a mechanical advantage for the springs 114 and 115 in applying contact pressure to the closed contacts.

As shown in FIGS. 20 and 21, a gear sector member is pivoted on a stud 126 attached to the rear housing member 9.. This gear sector member includes a pinion portion 127 having teeth meshing with the gear rack teeth 57 on the switch slide 28. The gear sector 125 also includes a gear portion 128 having teeth meshing with pinion teeth 129 formed on shaft 130. This shaft has a bearing portion extending into the housing member 9. It also extends forwardly through the plate 4 and carries a ratchet wheel 131 having ratchet teeth 132. The ratchet wheel 131 is preferably massive as shown and serves as a fly wheel for controlling the speed of movement of the gear rack 57. It will be apparent that upward or downward movement of the switch slide 28 will cause rotation of the gear sector member 125 about its pivot 126 and that this in turn will cause rotation of the ratchet wheel 131. It will also be apparent that the gearing provided is of the step up type causing the motion at the periphery of the ratchet wheel to be much greater than the up or down motion of the switch slide 28.

Referring to FIGS. 4 and 5, a holding pawl or latch member 133 is mounted on a stud 134 carried by the cross plate 4. This holding pawl 133 has an upper pointed portion i135 which is arranged to enter the slots 136 on the ratchet wheel 131. The preferred configuration of the ratchet wheel is shown enlarged in FIG. 20. The holding pawl 133 is formed with a hub portion 137 (FIGS. 1 and 6 adjacent plate 4 and this hub is surrounded by a torsion type spring 138 which serves to bias the holding pawl toward engagement with the ratchet wheel 136. The cross plate 4 is provided with an opening 140 through a lug 141 formed on closing pawl 133 extends. This lug extends into the path of the cam member 69 which is part of the switch operator 28.

The holding pawl 133 is also formed wth a lever section 142 which extends into engagement with the clapper 143 of a clapper type electro-magnet generally indicated 144. This electro magnet includes a frame 145 which is secured to the horizontal portion 5 of housing member 2. This frame 145 also has ears 146 extending into openings in the clapper 143. This provides a pivotal support for the clapper on the frame. This clapper is biased downwardly as seen in FIG. 4 by means of a biasing spring 147 and is held in position by retaining means 148 as well known in the art. It will be apparent that when the coil 149 of the electro-magnet 144 is energized, the clapper will be drawn upwardly against the force of the biasing spring 147. This will remove the free end of the clapper from engagement with the holding pawl 133 and thus permit this pawl to engage the ratchet wheel 131. When the coil 149 is deenergized, the spring 147 will pull the clapper 143 downwardly, this engaging the lever portion 142 of the holding pawl 133 for rotating it to disengage the ratchet wheel 131.

Power to the timer motor 112 is controlled by a timer motor switch generally indicated as 150. This switch consists of a lower relatively short switch blade 151 and an upper longer blade 152. These switch blades are suitably mounted on an insulating bracket 153 which is L-shaped as shown in FIG. 6, having one leg attached to the cross plate 4. These blades are biased down wardly and both ride a timer motor switch cam 155. As shown in FIGS. 1 and 24 the timer motor switch cam 155 is carried by the shaft 101 in front of the main cam 100. This switch cam is provided with a driving lub 156 which extends into a slot 157 formed in the main cam 100. The lug 156 and slot 157 provide a lost motion drive means for driving the switch cam 155 in controlled relationship with the cam 100. As shown in FIG. 2 the width of the slot 157 is greater than the lug 156, thus providing a lost motion drive between the two cams. In FIG. 2 and other figures the slot 157 and lug 156 are shown in full lines for clarity of illustration.

As shown in FIGS. 4 and 7 through 10, the switch cam 155 is provided with two separate camming portions or drop-offs 158 and 159. The drop-off 158 is located between two relatively low levels on the cam 155 and the drop-off 159 is located between two higher levels. In other words the two drop-offs are located at different levels or distances from the axis of rotation of the cam. As shown in FIG. 4, the cam 155 is positioned at a point where the short lower switch blade 151 has just dropped off the drop-off section 158. The longer blade 152 is still held up by the cam and this has caused the contacts on the two blades to be disengaged as shown. When the cam is rotated to the point where the upper blade 152 drops off, the contacts re-engage and only the lower blade rides the cam surface thus maintaining the contacts in engagement until the switch blades are separated at the next drop-off on the cam.

In addition to being operated by the cam 155, the switch 150 is also controlled by a lever 160 which is pivoted on a stud 161 mounted on the cross plate 4. As shown in FIG. 6, the lever 160 is formed with the hub 162 fitting over stud 161, the main portion of the lever extending adjacent the cross plate 4. At its outer end this lever is formed with an inward extension 163 which extends beneath the lower switch blade 151 for operating the same. As shown in FIG. 6 the electro-magnet clapper 143 is formed with an extension 165 which passes through a suitable opening in plate 4 and into a slot 166 in lever 160. As shown in FIG. 4 the electromagnet 144 is deenergized and the clapper 143 in its lower position. This has posiitoned the switch lever 160 to cause its operating portion 163 to be disengaged from the switch blade 151 thus allowing the motor switch contacts to be opened. When the electro-magnet 144 is energized, the upward motion of the clapper 143 raises lever 160 to close the motor switch 150.

FIG. 11 shows a typical wiring diagram for an air conditioning system in which applicants device is equipped with a line voltage timer motor. The three load switches 19 are separately connected to line wires 8 169, 170 and 171 and the other sides of the switches are connected to the three leads of the compressor motor 172. The timer motor switch 150 is connected to the input terminal receiving line wire 169 and the timer motor is connected to the input terminal receiving line wire 171. As shown in FIGS. 1 and 3 the input terminals for the two outer load switches are provided with auxiliary terminals 174 for facilitating connection of the timer motor circuit. The elector-magnet coil 149 is connected in circuit with a safety control orcontrols 173 and thermostat 174. Assuming conditions are correct in the system, the safety control 173 is normally closed and the thermostat 174 energizes the coil 149 on call for cooling and deenergizes it when the thermostat is satisfied. As shown in FIGS. 1 and 3 block 175 receiving terminals 176. This facilitates making external connections to the coil 149.

FIG. 13 shows a typical wiring diagram for a unit having a low voltage timer motor. In this diagram the load switches 19 are individually connected to the line wire 169, 170 nd 171 and also to the individual motor leads of the compressor motor 172. The timer 112 is connected into th low voltage circuit along with the coil 149. Preferably the safety control 173 controls power to the motor switch 150 and the thermostat 174 controls only the power to the electro-magnet coil 149.

OPERATION With the parts in the positions shown in FIGS. 1, 2 and 4, the control is in the Standby position awaiting the command of the thermostat 174 to call for compressor operation. In this position the cam follower roller 87 is at the top level of the cam 100 and the cam follower is at a position in which its lug 86 is above the latching surface 90 on closing pawl 60. At this time the switch operator 28 is in its upper position causing all of the switches to be open and the engaging surface 93 on closing pawl 60 bears against the lower surface of the switch block 6 which has caused this pawl to be at its clockwise limit of rotation with the latching surface 90 under abutment 86 on the cam follower. As the cam follower 80 is at the top of its stroke, the spring levers 117 are at their outer-most positions and springs 114 and 1 15 have been wound for a cycle of operation. The timer motor switch 150 at this time is open due to blade 151 having dropped down the drop-off 158 on the motor switch cam 155. The solenoid coil 149 is deenergized and thus clapper 143 and motor pawl 133 is held in disengaged position by clapper 143 and also by the switch operator cam 69.

When the thermostat 174 calls for cooling, it energizes the electro-magnet coil 149 which raises clapper 143 in turn operating the lever 160 which lifts switch blade 151 to close the timer motor switch 150. The parts are now in the positions shown in FIG. 7. The timer motor now runs and drives the camshaft assembly clockwise as seen in FIGS. 2 and 4. After approximately 15 seconds of timer motor operation (initial delay period) the cam follower roller 86 rides down the drop-off of the main cam this advancing the cam 100 approximately 90 which motion is permitted by the lug on the cam advancing in the slot 109 in gear 107. The downward motion of the cam follower and forward motion of the cam is caused by the spring lever rollers riding inwardly across the camming surfaces 88 of the cam follower 80.

During this downward motion of the cam follower, lug 86 on the follower engages the latching surface 90 ratchet wheel by thecamming surface 69 on the switch operator.

As the switch operator approaches the bottom of its stroke, the roller 119 on the lefthand spring lever 117 engages the releasing lever 92 on the closing pawl 89 causing this pawl to rotate clockwise toward releasing position. Also as the switch operator is lowered, the camming surface 69 releases the holding pawl 133 so that this pawl may move into engagement with the teeth on ratchetwheel 131. When the switch operator reaches the end of its design stroke, the latching surface 90'releases the lug 86 on the cam follower which is now held from returing by engagement of the holding pawl 133 with'the ratchet wheel 131. The design stroke of the cam follower is greater than that of the switch operator to allow for manufacturing variations. Thus after the closing pawl 89. is released the cam follower continues'downward allowing additional inward motion of the spring lever 117, this causing substantial clearance between the latching surfacs 90- and the lug 86 on the cam follower.

As the cam 100 advanced during the downstroke of the cam follower and switch operator, it also advanced the motor switch cam 155 due to lug 156 on cam 155 being engaged by the driving end of the slot 157 in cam 100; This caused the motor switch cam 155 to advance to the position shown in FIG. 8. At this time, the lower switch blade is riding the top level of the cam 155. The switch'contacts are'therefor closed and also the lower blade 151 has been lifted beyond the range of movement of the lever 160 At this time the driving lug 156 on cam 155 had advanced to the position shown and is in the path of the abutment 55 on switch operator 28.

Summarizing the operation thus far, the thermostat on call for cooling energized the electro-magnet which closes the timer motor switch as shown in FIG. 7. When the time motor runs approximately 15 seconds, the cam follower roller rides down the main cam which advances this cam and also the switch cam to the position of FIG. 8 in which the timer motor switch is maintained closed. During the downward motion of the cam follower, the closing pawl is engaged which pulls the switch operator downwardly against the action of its biasing springs and closes the main contacts. When the switch operator reaches the bottom of its stroke the closing pawl is disengaged and the holding pawl 133 engages the ratchet wheel 131 for holding the switch operator in contact closed porition. At the end of the closing stroke the parts assume the positions shown in FIGS. 8 and 12.

The timer motor will now continue to run and drive the gear 107 forwardly which is counterclockwise as seen in FIG. 22 which is a back view. Initially this movement of the gear will not cause rotation of the cams 100 and 155 as the pin 110 on cam 100 advanced in the slot 109 in the gear during the closing motion of the contact mechanism. After approximately two minutes of operation, the gear will have taken up the lost motion and have driven the cams I and 155 to the position shown in FIG. 9 where the lower switch blade 151 has dropped off the high drop-off section 159 on cam 155. This causes the motor switch 151 to open as shown. The motor switch opens at this time even though the electro-magnet is energized due to the cam now having moved the motor switch beyond the range of movementof the electro-magnet operated lever 160.

The control mechanism will remain in this condition with the main switches closed and timer motor switch open as long as the thermostat continues to call for cooling. When the thermostat becomes satisfied, it opens the circuit to the coil 149 of the electro-magnet and its clapper 166 drops as shown in FIG. 10. This dropping of clapper 166 rotated the holding pawl clockwise releasing it from the ratchet wheel 131. This allows the biasing springs 95 and 96 to raise the switch operator to its upper position as shown in FIG. 2 where the main switches are again opened, this stopping the compressor. On initial upward motion of the switch operator the cam 69 which is part of the operator engaged the extension 141 of the holding pawl 133to hold it released from the ratchet wheel 131. The purpose of this arrangement is to prevent damage to the ratchet wheel or holding pawl in the event the electromagnet should become energized during the opening stroke of the switch operator. It also insures a complete opening stoke of the switch operator anytime the electro-magnet is deenergized and avoids any possibility of the switches becoming locked in a partially open position.

Also during the opening stroke of the switch operator, the camming abutment 55 of this operator engages the driving lug 156 of the motor switch cam 155. This advanced the switch cam 155 from the position shown in FIG. 9 to the position shown in FIG. 10 in which the motor switch 150 is reclosed. As this switch is in sole control of the timer motor, the timer motor 112 will now operate and drive the camshaft assembly back to the point shown in FIGS. 2 and 4. At this time the lower switch blade 151 of the timer motor swithc drops down the lower drop-off section 158 of the cam 155.

When the switch operator 28 reached the top of its stroke the engaging lever portion 93 of the closing pawl 89 became in contact with the lower surface of the switch block as shown in FIG. 14. This rotated the holding pawl clockwise bringing the latching surface 90 back into the path of the lug 86 on the cam follower 80. As the cam follower is raised by cam the lug 86 on this follower engages the camming surface 91 on the closing pawl which forces the closing pawl out of the path of the lug. This motion is allowed by a slight downward motion of the switch operator 28 against the action of its biasing springs. As the cam follower rises, it cams the spring levers 117 outwardly rewinding springs 114 and 115 for the next cycle. As the follower reaches the top of its stroke the lower edge of the lug 86 clears the latching surface 90 of the holding pawl which permits the holding pawl to be rotated to the position shown in FIG. 2 by the action of the engaging lever section 93 on the lower surface of th switch block 6. The control system is now ready for the next cycle of operation when the thermostat calls for cooling.

Summarizing the operation on call for cooling the thermostat energizes the electro-magnet which closes the timer motor switch starting the timer motor. Afer 15 seconds of timer motor operation, the cam follower rides down the incline ofthe cam which pulls the switch operator to closed position due to the holding pawl being engaged. At the end of th switch operator stroke the holding pawl is released and the switch operator is held in closed position by the holding pawl. During this main switch closing action, the timer motor switch is maintained closed independently of the electro-magnet and the timer motor will run for approximately two minutes being stopped by reopening of the motor switch. When the thermostat is satisfied it denergizes the electro-magnet which releases the holding pawl allowing the biasing springs to raise the switch operator for opening the main switches. This opening movement of the switch operator 28 reclosed the timer motor switch for restarting the timer motor. Approximately five minutes after this occurs the cam follower has been raised, storing power in a spring means for the next cycle. The timer motor switch 3 opens and the electromagnet is once again conditioned for reclosing the switch on call for cooling by the thermostat.

It should be noted that in the arrangement described, power from the timer motor is stored in a spring means which is available to operate the switch closing means under the command of the thermostat. Also when the switch is closed, the switch closing means is released so that the switch opening means can open the switches instantly without requiring any operation from the timer motor. When the switch opening means operates by release of the holding pawl on the ratchet wheel the switch opens and once the opening movement is started it continues for the full stroke. It should also be noted that the linkage between the switch operator and the holding pawl provides a considerable mechanical advantage to the holding pawl in holding the switch operator in closed position. This lowers the force on the holding pawl and consequently it can be released by a small force from the electro-magnet even though the opening force on the switch operator is considerable.

From the foregoing it will be apparent that the present invention provides a simplified control system which is especially useful in air-conditioning or refrigeration systems where time delays are desirable. While the invention is of particular utility in such systems it is not limited thereto as many features have uses in other applications. As many modifications may be made in the construction and application of the invention it is desired to be limited only by the scope of the appended claims.

I claim:

1. In a control mechanism, a switch, cam means arranged to operate said switch, an operator, means for supporting said operator and providing a limited range of movement therefor said operator being arranged to operate said switch conjointly with the cam means, said cam means having two separate camming portions at different levels for operating the switch, the camming portion at one level being within the range of movement of the operator providing conjoint operation of the switch, and the camming portion at the other level being beyond the range of movement of the operator to exclude operation of the switch by the operator.

2. The combination recited in claim 1 in which the cam means is constructed and arranged to actuate the switch in one direction at a predetermined position of the camming portion at said one level of the cam means, and the operator is construced and arranged to actuate the switch in the opposite direction, said cam means and switch also being constructed and arranged to enable the cam means to operate the switch in both directions at predetermined positions of the camming portion at the other level of the cam means.

3. The combination recited in claim 1 in which the switch consists of two cooperating blades each riding the cam means and the two camming portions of the cam means provide two drop-off sections, said blades and cam means being constructed and arranged to cause one blade to drop while holding the other at each of the drop-off sections, one drop off section being within the range of movement of the operator and the other drop-off section being beyond said range of movement. 

1. In a control mechanism, a switch, cam means arranged to operate said switch, an operator, means for supporting said operator and providing a limited range of movement therefor , said operator being arranged to operate said switch conjointly with the cam means, said cam means having two separate camming portions at different levels for operating the switch, the camming portion at one level being within the range of movement of the operator providing conjoint operation of the switch, and the camming portion at the other level being beyond the range of movement of the operator to exclude operation of the switch by the operator.
 2. The combination recited in claim 1 in which the cam means is constructed and arranged to actuate the switch in one direction at a predetermined position of the camming portion at said one level of the cam means, and the operator is construced and arranged to actuate the switch in the opposite direction, said cam means and switch also being constructed and arranged to enable the cam means to operate the switch in both directions at predetermined positions of the camming portion at the other level of the cam means.
 3. The combination recited in claim 1 in which the switch consists of two cooperating blades each riding the cam means and the two camming portions of the cam means provide two drop-off sections, said blades and cam means being constructed and arranged to cause one blade to drop while holding the other at each of the drop-off sections, one drop off section being within the range of movement of the operator and the other drop-off section being beyond said range of movement. 